Create fake session to write csp nonces to it

`Csp::createnonces()` writes to a window aware session and hence a fake base session
is created in `BaseTestCase::setUp()` method

library/Icinga/Application/Test.php

@@ -75,6 +75,7 @@ class Test extends Cli
 
         // Conflicts with `Tests\Icinga\Module\...\Lib`. But it seems it's not needed anyway...
         //$this->getLoader()->registerNamespace('Tests', $this->getBaseDir('test/php/library'));
+        $this->getLoader()->registerNamespace('Tests\\Icinga\\Lib', $this->getBaseDir('test/php/Lib'));
 
         return $this;
     }

library/Icinga/Test/BaseTestCase.php

@@ -4,8 +4,10 @@
 namespace Icinga\Test {
 
     use Exception;
+    use Icinga\Util\Csp;
     use Icinga\Web\Request;
     use Icinga\Web\Response;
+    use Icinga\Web\Session;
     use ipl\I18n\NoopTranslator;
     use ipl\I18n\StaticTranslator;
     use RuntimeException;
@@ -14,6 +16,7 @@ namespace Icinga\Test {
     use Icinga\Data\ConfigObject;
     use Icinga\Data\ResourceFactory;
     use Icinga\Data\Db\DbConnection;
+    use Tests\Icinga\Lib\FakeSession;
 
     /**
      * Class BaseTestCase
@@ -108,6 +111,8 @@ namespace Icinga\Test {
             parent::setUp();
             $this->setupRequestMock();
             $this->setupResponseMock();
+            Session::create(new FakeSession());
+            Csp::createNonce();
 
             StaticTranslator::$instance = new NoopTranslator();
         }

test/php/Lib/FakeSession.php

@@ -0,0 +1,29 @@
+<?php
+
+namespace Tests\Icinga\Lib;
+
+use Icinga\Web\Session\Session;
+
+class FakeSession extends Session
+{
+    public function read()
+    {
+    }
+
+    public function exists()
+    {
+    }
+
+    public function purge()
+    {
+    }
+
+    public function refreshId()
+    {
+    }
+
+    public function getId()
+    {
+        return '1234567890';
+    }
+}